Material Coating on Magnet, Hci vs Hcb, Pole piece function

[metalparts]

Dear all!

I have question about the coating materials. Currently, the applied coating for magnets of our company are Ni, Cu-Nib 10, Zn. Some people said the Zn itself is not as strong as Ni and Cu-Nib(the coating thickness stays the same: 10 mic) Is that correct?

Regarding to the coating cost, can epoxy or Parylene coating be cheaper? pls suggest me.

The other thing is about the Hci & Hcb. I am pulzzed about Hci function? and what is the difference b/w Hci and Hcb? pls kindly explain.(i am a dummy, pls make it simple =.=)

One thing is about the Pole Piece (using the Headphone capsule), i learnt that actually, the Pole piece is just a metal piece whose function is to bend the magnectic field from straight line to contangent curve, is it correct? or some other function is missing? pls help me check this one (this description may be a little unclear, pls feel free to ask me if u do not understand what i am talking ^^)

 

[EdStainless]

The pole piece is used to shape the field and allow you to use simple shaped magnets. The saturation level of the pole piece (B x cross section) needs to be greater than that of the magnet or you will saturate it and not all of your filed will be focused where you intended.

The coating depends on expected life and other factors. I always liked Parylene.

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Plymouth Tube

 

[metalparts]

Thanks EdStainless for your kind help. Now i know the main function of the pole piece, but there are some questions not be explained yet, pls advise me